This invention relates to substances useful for accelerating or promoting the growth of plants, which substances are derived from the hyphae of edible fungi such as shiitake and whose main effective ingredient is germanium present in the form of organic compounds, and also to the manufacture of the same.
Germanium, the atomic number of which is 32, occurs in nature in the form of certain compounds in various parts of the earth. It has a bright grey color, is hard and brittle and has a metal-like appearance. Actually, it is a semiconductor and finds extensive applications in the electronic field, particularly for amplification and modulation purposes, as is well known in the art.
In the mean time, germanium is known to be contained in coal, and hence in vegetation. Also, it is found that germanium is contained in great quantities in any of bamboo grasses, new shoots of tea and leaves of oak (as reported in Asai Germanium Research Institute Report Vol. 1, issued in December, 1971). Further, some plants valuable in medicine have the following germanium contents (as stated in the same report).
______________________________________ Aloe 77 ppm Comfrey 152 ppm Chlorella 76 ppm Garlic 754 ppm Bandai udo 72 ppm Bandai mushroom 255 ppm ______________________________________
By the way, it is said that in Korea there are few people suffering from cancer. This is thought to have a close bearing upon the fact that garlic is a daily food there, the aforementioned surprising germanium content in the garlic perhaps playing an important role in keeping cancer in check.
The aforesaid report further gives results of research concerning the relation between germanium and growth of plants. It says that marked differences are noted in the growth and flavor between ginseng sprayed with a dilute water solution of some complex salt of germanium and an unsprayed one, and that germanium is a must for the growth of plants. Regarding the causes for these differences, the report explains that the ginseng is perhaps very susceptible to numerous viruses and bacteria present in the soil and readily attacked by these enemies under the usual circumstances, but by taking in germanium it will produce a powerful arm (probably some biocatalysts or enzymes) which is well able to cope with and destroy the enemies.
Despite the fact that germanium is very important for the growth of plants, the conventional method of cultivation has had an inherent problem that the yield of the seed or fruit crop has been unsatisfactory in spite of the flourishing growth of stalks and leaves.
As a typical example, the yield of soybeans is very low in Japan. This is due, at least partly, to the fact that the productivity of this crop plant there is too low to let this crop stand in the international competition and that unlike rice and sugar beet no government help has heretofore been given to this crop. After all, the yield of this crop, unlike rice, has not been substantially improved for the last several decades. In fact, the average yield of the soybean is 11 to 14 kilograms per acre and has not been practically increased since about 1930. On the other hand, the yield of rice, which was below 30 kilograms per acre in the 1930's, is now about to exceed 50 kilograms per acre. Among the factors for the obstructed improvement of the yield of the soybean is the fact that this crop plant is poorly sensitive to manuring. The poor sensitivity of a plant to manuring means its tendency to permit little increase of the yield by increasing the manure. In Hokkaido, it is customary to give only 0.05 to 0.2 kilograms per acre of nitrogen as manure. This quantity is required to ensure the growth in the initial stage. However, the supply of further nitrogen is not thought to be needed for fixed nitrogen is taken in from the root; rather, it is thought to be wasteful since it merely promotes the growth of stalks and leaves. For this reason, few attempts to increase the yield by improving the way of supplying nitrogen have been reported. Similarly, no pronounced increase of yield is obtainable by increasing the amounts of phosphoric acid and potassium supplied, and hence there are few reports on relevant experiments and research. ("Soybeans Culture Technical Data," No. 3, 1974, issued by General Department, Shizai Engei Headquarters, Zenno)
Before the instant invention, the inventors had been studying the hyphae of edible fungi for many years. Particularly, they were interested in the metabolic products and liquids in the cells of these hyphae and made extensive experiments concerning the utility and method of extraction of these substances. As a result, they found that liquid extracts produced through self-digestion of the hyphae with enzymes resulting from the metabolic process in the hyphal body, i.e., .beta.-1-3 glucanase and chitinase, had the effects of reducing blood pressure and holding cancer in check and also served as an effective herbicide for moss.
The inventors endeavored in further investigations and researches to expand the above findings, and they casually obtained markedly better growth of soybean, eggplant, tomato and other crop plants by spraying the leaves of these plants with a dilute solution of a liquid extract derived from the hyphae of shiitake. Particularly, the yield of the soybean could be surprisingly increased. Theoretically, it was impossible to attribute this result to the effect of the sole self-digestion liquids resulting from self-digestion with .beta.-1-3 glucanase and chitinase. In an effort to clarify the causes, it was assumed that germanium, which was known to be taken in many plants, had something to do with the facts that the liquid extract obtained from the hyphae of shiitake was turned into a white emulsion by adding hydrochloric acid, that the extract had the effect of suppressing cancer and that the fruiting body of shiitake extended its height and cap dimension to surprising extents overnight. As a result of analysis of that liquid extract, organic germanium was found to be present in that liquid. It was thought that the germanium was present not as such, i.e., not in the form of the element, but in the form of complex salts with polysaccharides in the metabolic liquids in the hyphal cells.
The present invention is predicated on the foregoing findings, and it seeks to provide novel uses of the organic germanium component in the hyphae of edible fungi.